Compilare: main.cpp: In function 'std::stack<int> topologicalSortUtil(const std::vector<std::vector<int> >&, int, std::stack<int>&, std::vector<bool>&)': main.cpp:14:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < graph[current].size(); i++) { ~~^~~~~~~~~~~~~~~~~~~~~~~ main.cpp: In function 'std::stack<int> topologicalSort(const std::vector<std::vector<int> >&)': main.cpp:26:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < graph.size(); i++) { ~~^~~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:36:39: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("sortaret.in", "r", stdin); ^ main.cpp:37:41: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("sortaret.out", "w", stdout); ^ main.cpp:39:26: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ main.cpp:44:34: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &src, &dst); ^